Nonlinear Susceptibility in Semiconductor hetrostructures

The linear and non-linear optical properties of three-level systems get a great importance from both theoretical and experimental points of view. This is due to the phenomena related to these systems, like electromagnetic induced transparency (EIT), coherent population trapping (CPT) and coherent adiabatic population (CAP). In contrast to CPT which is a‘‘spectroscopic’’ phenomenon that involves only modifications to the material states in an optically thin sample, EIT is a phenomenon specific to optically thick media where both the optical fields and the material states are modified The importance of EIT stems from the fact that it gives rise to greatly enhance non-linear susceptibility in the spectral region of induced transparency of the medium and is associated with steep dispersion.